Introduction
Nature Medicine 12, 1259–1268 (2006); published online 22 October 2006.
In page 1264 of this article, it is stated that "The donor cells were dispersed over an average radius of 1.6 
0.6 mm, and the mean number of HNA+ nuclei/mm3 within each was 136,726 23,515". The authors wish to clarify that they used the word "radius" in the non-geometric sense, as in this definition of the American Heritage Dictionary: "A bounded range of effective activity or influence". At the same time, they want to remark that the numbers, figures and scale bars shown in the paper are correct.